The present invention relates generally to semiconductor devices, and, more particularly, to the sensing or detection of ionizing radiation in semiconductor devices.
Ionizing radiation can cause single event upsets (“SEUs”) or “soft errors” in semiconductor integrated circuits (“ICs”). In general, there exist multiple radiation sources that affect the proper operation of ICs. These may comprise, for example, alpha particles from packaging materials (e.g., lead or lead-free solder bumps) or impurities introduced in wafer processing. Other radiation sources include daughter particles from terrestrial cosmic ray neutron collisions, energetic heavy ions in a space environment, and daughter particles from proton collisions in a space environment (e.g., trapped proton belts).
Ionizing radiation can directly upset storage circuits, such as SRAMs, register files and flip-flops. Undesirable memory cell bit state flips or transitions between binary logic states have occurred for years, and error checking and correction (“ECC”) techniques are typically used to correct for any radiation-induced errors in the memory cells. More recently, as combinational logic has scaled down in size, radiation events create voltage glitches that can be latched by such logic circuits. In general, SEUs may cause the IC to perform incorrect or illegal operations.
Methods to prevent SEUs include adding spatial and/or temporal redundancy within the semiconductor device, so that a single radiation event cannot cause an SEU therein. However, redundancy solutions incur area, power and performance penalties. It is known to use relatively small detectors or sensors as part of the IC to detect radiation that is relatively uniform. However, the radiation environment for commercial and space applications typically comprises discrete events, localized in time and space, rather than a uniform dose of radiation spread across the IC. Thus, the known devices cannot detect the more common radiation environment consisting of individual events.